CA1320748C - Inclination measuring device and a capsule therefor - Google Patents
Inclination measuring device and a capsule thereforInfo
- Publication number
- CA1320748C CA1320748C CA000527960A CA527960A CA1320748C CA 1320748 C CA1320748 C CA 1320748C CA 000527960 A CA000527960 A CA 000527960A CA 527960 A CA527960 A CA 527960A CA 1320748 C CA1320748 C CA 1320748C
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- Prior art keywords
- capsule
- electrodes
- liquid
- temperature
- inclination
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C33/00—Unsaturated compounds having hydroxy or O-metal groups bound to acyclic carbon atoms
- C07C33/28—Alcohols containing only six-membered aromatic rings as cyclic part with unsaturation outside the aromatic rings
- C07C33/30—Alcohols containing only six-membered aromatic rings as cyclic part with unsaturation outside the aromatic rings monocyclic
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C9/00—Measuring inclination, e.g. by clinometers, by levels
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
- A61P11/00—Drugs for disorders of the respiratory system
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
- A61P11/00—Drugs for disorders of the respiratory system
- A61P11/08—Bronchodilators
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- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
- A61P17/00—Drugs for dermatological disorders
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
- A61P29/00—Non-central analgesic, antipyretic or antiinflammatory agents, e.g. antirheumatic agents; Non-steroidal antiinflammatory drugs [NSAID]
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
- A61P43/00—Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
- A61P9/00—Drugs for disorders of the cardiovascular system
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- C07C323/00—Thiols, sulfides, hydropolysulfides or polysulfides substituted by halogen, oxygen or nitrogen atoms, or by sulfur atoms not being part of thio groups
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- C07C59/00—Compounds having carboxyl groups bound to acyclic carbon atoms and containing any of the groups OH, O—metal, —CHO, keto, ether, groups, groups, or groups
- C07C59/40—Unsaturated compounds
- C07C59/42—Unsaturated compounds containing hydroxy or O-metal groups
- C07C59/48—Unsaturated compounds containing hydroxy or O-metal groups containing six-membered aromatic rings
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
- C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
- C07D213/24—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with substituted hydrocarbon radicals attached to ring carbon atoms
- C07D213/28—Radicals substituted by singly-bound oxygen or sulphur atoms
- C07D213/30—Oxygen atoms
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
- C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
- C07D213/24—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with substituted hydrocarbon radicals attached to ring carbon atoms
- C07D213/54—Radicals substituted by carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals
- C07D213/55—Acids; Esters
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- C07D303/00—Compounds containing three-membered rings having one oxygen atom as the only ring hetero atom
- C07D303/02—Compounds containing oxirane rings
- C07D303/38—Compounds containing oxirane rings with hydrocarbon radicals, substituted by carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals
- C07D303/40—Compounds containing oxirane rings with hydrocarbon radicals, substituted by carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals by ester radicals
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
- C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
- C07D307/34—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
- C07D307/38—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with substituted hydrocarbon radicals attached to ring carbon atoms
- C07D307/40—Radicals substituted by oxygen atoms
- C07D307/42—Singly bound oxygen atoms
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- C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
- C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
- C07D307/34—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
- C07D307/38—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with substituted hydrocarbon radicals attached to ring carbon atoms
- C07D307/54—Radicals substituted by carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D309/00—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only ring hetero atom, not condensed with other rings
- C07D309/16—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only ring hetero atom, not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member
- C07D309/28—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only ring hetero atom, not condensed with other rings having one double bond between ring members or between a ring member and a non-ring member with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D309/30—Oxygen atoms, e.g. delta-lactones
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- C07D—HETEROCYCLIC COMPOUNDS
- C07D405/00—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom
- C07D405/02—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom containing two hetero rings
- C07D405/06—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom containing two hetero rings linked by a carbon chain containing only aliphatic carbon atoms
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- C07K—PEPTIDES
- C07K5/00—Peptides containing up to four amino acids in a fully defined sequence; Derivatives thereof
- C07K5/04—Peptides containing up to four amino acids in a fully defined sequence; Derivatives thereof containing only normal peptide links
- C07K5/06—Dipeptides
- C07K5/06008—Dipeptides with the first amino acid being neutral
- C07K5/06017—Dipeptides with the first amino acid being neutral and aliphatic
- C07K5/0606—Dipeptides with the first amino acid being neutral and aliphatic the side chain containing heteroatoms not provided for by C07K5/06086 - C07K5/06139, e.g. Ser, Met, Cys, Thr
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C9/00—Measuring inclination, e.g. by clinometers, by levels
- G01C9/02—Details
- G01C9/06—Electric or photoelectric indication or reading means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C9/00—Measuring inclination, e.g. by clinometers, by levels
- G01C9/18—Measuring inclination, e.g. by clinometers, by levels by using liquids
- G01C9/20—Measuring inclination, e.g. by clinometers, by levels by using liquids the indication being based on the inclination of the surface of a liquid relative to its container
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- Cardiology (AREA)
- Rheumatology (AREA)
- Dermatology (AREA)
- Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
- Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
- Investigating Or Analyzing Materials Using Thermal Means (AREA)
Abstract
ABSTRACT
A sensor for an inclination measuring device is disclosed which comprises a capsule part-filled with a conductive liquid. First to fourth electrodes A-D are disposed within the capsule in contact with the liquid.
An electrical signal is applied between electrodes C, D
and one then the other of electrodes A, B, to derive a signal indicative of the degree of immersion of the electrode A, and then the electrode B within the liquid. The ratio of these signals is related to the angle of inclination of the capsule about the reference axis O and relative to a first reference angle defined at the gap between the electrodes A, B.
The capsule 1 is also constructed to compensate for thermal effects. by forming the sides of the capsule so that they are responsive to pressure change within the capsule caused by thermal expansion of the contents of the capsule to expand the volume of the capsule, to keep the level of liquid therein constant.
A sensor for an inclination measuring device is disclosed which comprises a capsule part-filled with a conductive liquid. First to fourth electrodes A-D are disposed within the capsule in contact with the liquid.
An electrical signal is applied between electrodes C, D
and one then the other of electrodes A, B, to derive a signal indicative of the degree of immersion of the electrode A, and then the electrode B within the liquid. The ratio of these signals is related to the angle of inclination of the capsule about the reference axis O and relative to a first reference angle defined at the gap between the electrodes A, B.
The capsule 1 is also constructed to compensate for thermal effects. by forming the sides of the capsule so that they are responsive to pressure change within the capsule caused by thermal expansion of the contents of the capsule to expand the volume of the capsule, to keep the level of liquid therein constant.
Description
This invention relates to a device and, more particularly, but not exclusively to a sensor for an electronic level or inclina~:ion gauge.
Optical levels, more commonly called spirit levels, are well known and provide an optical indication of whether or not a sur~ace is horizontal, based on the principle of an air bubble in a liquid-filled vial always seeking the highest point in the vial, the vial being slightly curved so that ~hen at level, the bubble will always take up an equilibrium position. Such bubble levels, if disposed in a suitable ~eame, can also be used to provide an indication of whether or not a surface is vertical.
However, such spirit levels are not capable of measuring deviations ~rom horizontal or vertical outside a very limited range. Also, such spirit levels can be difficult to read accurately as the measurement of level or plumb depends on the ability of the user to determine the position o~ the bubble. Factors such as poor lighting or poor eyesight obviously affect this.
1 3207~8 Electronic spirit levels have been proposed, for example by Cantarella, in U.S. 4 167 818, which uses a capsule part-filled with a conductive liquid. Several electrodes are disposed within the capsule, the resistance between the electrodes being dependent of the position of the liquid within the capsule which, in turn, is dependent upon its inclination. A digital readout of angles of inclination from level and from plumb is provided. However such levels suffer the disadvantage that the accuracy of any measurement from horizontal or vertical is dependent: upon ambient conditions such as temperature, as fluctuations in temperature will lead to variations in the level and resistance of liquid within the capsule which in turn will affect the reading of inclination for angles for which the electrodes are not equally immersed in the liquid.
GB-A-2 071 887 discloses a microwave oven with a separate temperature sensor (28) comprising a bellows (60) and a liquid of a high coefficient of thermal expansion sealed inside, and a sound generating body (54). When the liquid (59) is expanded by heating, the bellows (60) is stretched, causing the sound-g~nerating body (54) to generate a sound which is received by the microwave oven.
GB-A-2 048 473 discloses a thermostat capsule comprising a can (1) of stainless steel with an annular end plate (2) closed by a diaphragm (3). The can (1) is filled with liquid which causes the dapth of the can (1~ to vary with temperature.
US-A-4 028 815 discloses an accelerometer or tilt sensor. It comprises a closed chamber of annular configuration, four electrodes and electrolytic fluid, in conjunction with circuitry arranged to produce an output signal compensated 1 32074~
for temperature variations in impeclance and volume of the fluid.
EP-A-0 035 340 discloses a clinometer comprising a hollow cylindrical housing (10) having a single electrode (12) on one end face and three equal, equally spaced, electrodes (14, 16, 18) on the other end faceO The effects o~ temperature variation are not discussed in it.
According to the invention in a first aspect there is provided an electronic inclinometer incorporating temperature-compensating means and comprising a capsule which is formed as a hollow cylinder and which is part-filled with a liquid, the liquid being such as to vary in volume with variation in temperature, and a plurality oE electrodes connected to the capsule for sensing an electrical characteristic of the liqu.id, said characteristic being one which varies with variation in inclination of the capsule, over at least a certain range of inclination, about a reference axis, so that the inclinometer has an elactrical transfer function which is a function of inclination angle, characterized in that the material and wall thickness of the cylindrical side wall of the capsule are such that the cylindrical side wall does not significantly change dimensionally in response to temperature-induced change in pressure within the capsule and in that the material and wall thickness of each of the end walls are such that the end walls do deform elastically in response to said temperature-induced change in pressure within the capsule so that the internal volume of the capsule is variable in dependance upon temperature, to such an extent that the level of the liquid in the capsule remains substantially constant for any given inclination within said range of inclination with variation in temperature over at least a certain range of temperature.
~' 1 32074~
3a In preferred embodiments: the capsule is formed from plastics material~ more preferably, polybutylene therephthalate, which may be reinforced with glass beads; and the liquid includes methanol.
In further prefsrred embodiments: the capsule comprises first and second mouldings connected together; the capsule may also comprise a hollow cylindrical member and first and second discs, each disc being connected to a respective end of the cylindrical member. The electronic inclinometer may further comprise switch means for connecting the electrodes in a plurality of desired configurations, the s~itch means having an electrical transfer function which i5 a function of temperature. Compensation may be provided for the dependance on temperature of the combined electrical transfer function of the capsule and switch means over the temperature range~
The plurality of electrodes may include first and second electrodes disposed within the capsule, the relative degree of immersion of the first and second electrodes in the liquid ~0 being indicative, within a first angular range, of the angle of inclination of the capsule both about the reference axis and relative to a first reference angle. Further the plurality of electrodes may include third and fourth electrodes disposed within the capsule, the relative degree of immersion of the third and fourth electrodes in the liquid being indicative, within a second angular range~ of the angle of inclination of the capsule both about the reference axis and relative to a second reference angle different from the first reference angle. Moreover, the first and second reference angles may be those at which the first and second electrodes or the third and fourth electrodes, respectively, are equally immersed in the liquid. The first to fourth electrodes may be arranged so tha-t any angle of inclination 3b of the capsula about the reference axis is included within at least one of the first and second ranges. The first and second reference angles may be orthogonally disposed. The first to fourth electrodes may be of substantially semi-circular form and may be spaced one from the other about the raference axis.
According to the invention there is also provided but not claimed in this application a method of calibrating an inclination sensor of the form co~)rising a capsule part filled with a liquid, the position of the liquid within the capsule being indicative of the angle of rotation of the capsule about a reference axis, a plurality o electrodes disposed within the capsule for sensing said position within an angular range, an excitation source, a sensing circuit and means for connecting said electrodes to the sensing circuit and to the excitation ~ource allow measurement of a plurality of electrical characteristics of the liquid which together are indicative of said position, said method comprising the steps of placing the sensor at at least two ~nown angles ~ , measuring the corresponding sensed angles 0 and calculating from the known and sensed angles calibration values a and b where;
O = a ~ + b An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a perspective view of a sensor capsule forming part of an embodiment of the invention;
Figure 2 is a sectional view taken in the plane II~
of Figure l;
1 3207~8 Figure 3 i6 an exyloded sectional view taken through the plane III-III' of Figure l;
Figures 4A-B are sectional views similar to Figure 2 of the capsule at different inclinations;
Figure 5 illustrates the angular range of the sensor.
Fig 6 is a diagram for explaining the effec~ of change in liquid level on capsule sensitivity.
Figure 7 illustrates the ability of the capsule shown in Figures 1 to ~ to compensate for temperature fluctuations.
Figures 8 and 9 are diaqrams illustrating features of the design calculations for calculating a preferred capsule wall thickness, for temperature compensa~ion purposes.
Pigure 10 is a diagram for explaining the effect of switch resistance on capsule sensitivity.
1 3~07~8 Referring to Figures 1 to 3, an inclination sensor, generally designated 1 is shown. The sensor comprises a capsule 3 of generally cylindrical form. The capsule 3 is formed from two engageable non-conductive chemically inert plastics mouldings 5,7 formed preferably from thermoplastic polyester (e.g. a polybutylene terephthalate (PBT) for example VALOX) reinforced with 15-20% glass beads to provide strength and stability.
The mouldings 5, 7 are ultra-sonically welded together to ensure a hermetic seal. The end faces 9,11 of the mouldings 5,7 are formed of a thickness so as to be elastically deformable in response to pressure variations within the capsule 3, as described hereinafter.
Within mouldings 5,7. electrodes A,B and C,D formed from nickel are respectively disposed. Each electrode A-D is of generally semi-circular form and is formed on its respective moulding 5,7 preferably by vacuum deposition or ho~ foil blocking (although it is to be appreciated that other electrode-forming methods may be employed).
The electrodes A,B (or C,D) are separated one from the other by an elongate gap 8 (or 10) so that the electrodes A,B or C,D are not in direct electrical 1 32074~
contact. The gaps 8,10 should be narrow, preferably less than 0.5 mm. Connections to the lelectrodes A-D are provided by means o~ rivets formed from conductivQ plastics material.
which are bonded, preferably by ultra-sonically welding to the case halves; rivets 13,15 for electrodes A,B are shown in Figure 2.
Alternatively, the capsule may be formed from two identical plastics discs, the eleckrodes being formed on the discs by silk screen printing, each disc then being connected to an open axial end of a hollow cylindrical plastics spacer. to form the capsule, the discs being rotated by 90~ relative to one another to give the desired electrode configuration shown in figure 1.
The electrodes A,B are rotated by 90 about a reference axis 0 of the capsule with respect to the electrodes C,D to allow measurement of angles through 360 as described hereinaft~r.
A conductive liquid 17 is disposed within the capsule 3, preferably a mixture of distilled water and methanol and a salt, for example sodium acetate trihydrate (CH3 COONa 3H2O), the capsule 3 being filled, at NTP to half its volume. The remainder of the capsule is filled with air or an inert gas, for example argon.
1 32~74~
The general mode of operation of the capsule is described with reference to Figures 4A and ~B for which a measurement using electrodes A,B as the sensing electrodes is illustrated. Figures 4~ and 4B illustrate the capsule 3 in a schematically shown mounting 19 having an edge 21 which is presented to a surface, the inclination of which is to be measured. One pair of electrodes in this case C,D are coupled together to form a common electrode and an alternating voltage is applied in turn to the electrodes A or B. The impedance and, more particularly, the resistance of the path between electrodes C,D and electrode A or electrode B is dependent upon the degree of immersion of electrode A or electrode B in the conductive liquid 17, the larger degree of immersion, the lower the resistance of the path.
Thus by measuring the resistances of the two paths, between electrodes C,D and electrode A and electrodes C,D and electrode B, the angle o~ inclination ~ of the sensor can be calculated.
,~
1 3207~
More specifically as can be seen by comparison of Figures 4A
and 4B, the total wetted area of electrodes A,B is always substantially a constant, so that, ignoring cross impedances:
ZT Zl Z2 WHERE ZT = The total tesistance of the capsule Zl = The resistance of the path CD to A
Z2 = The resistance of the path CD to B
AND Zl 180 , ZT ... lb 90 + ~
Z2 ~ 180 . ~T ... lc S so - e So, the ratio, R, of the resistances Z1, Z2 is:
...2 2 9o +
hence ~ = go (1 - ~ . 3 ~1 + Rj 1 32074~
Exemplary values of R are as follows:
Table 1 ~ R = ,L
- 50 3.5 1() 0 + 45 0.33 + 50 0.286 Electrodes A,B are used for sensing angles up to t 50 from the hori70ntal in the configuration illustrated in Figures 4A and 4B. For angles of inclination greater than these limits, the electrodes may be reconfigured so that the electrodes A,B become the common electrode and the orthogonally disposed electrodes C,D become the sensing electrodes. the sensor measuring angles in this configuration in the range ~ 50 from vertical.
1 3207~8 Reconfiguring the electrodes may conveniently be performed using a switch matrlx comprising a plurality of analogue switches, for connecting each electrode to an alternating voltage source or to sensing circuitry in common with another electrode, as appropriate.
Use of such electrode switching allows a full 360 of inclination angle to be measured, in terms o~ deviation from level or plumb, (as shown in Figure 5) with the electrode configuration being chosen by computing and control circuitry (not shown) in accordance with the angle of inclination of the sensor. When initialising an inclination measurement, the control circuitry may perform a measurement with an arbitrary pair of electrodes e.g. C,D chosen as the common pair. If the 1~ ratio R calculated by the computing circuitry is within an allowable range (~ 50) (see Table 1), the measurement proceeds whereas if the measured ratio is outside the allowable range, the configuration is changed to connect the other pair of electrodes in common, and the measurement is then performed.
In the described capsule, the volume of the liquid 17 within the capsule 3 is prone to fluctuation with temperature. Due to volume changes arising from differing thermal expansion of the capsule and the liquid, changes in temperature will result in changes in liquid level which will affect: the measurement of inclination. This e~ect is shown with reference to figure 6.
Assuming an increase in liquid level, in response to temperature. Is indicated by change in height x .
Then, let ST be the ~total' conductivity of the half filled capsule:
I -T
~'1' ;' where ZA~ ZB are the resistances of paths CD to A
and CD to B.
1 32074~3 ~z~ ~A SA + SA ~ ~ +~~ + ~ ~ ] ' 5 = S~ E + e + ~1 ... 6 ~ l 90 ~r~
where SA* = the conductance due to plate area A
immersed in the liquid SA = the conductance due to plate area A' immersed in the liquid similarlY Sg = S~ E _ 9O + ~r~ 7 Now R =
Combining 6, 7 and 8 and rearranging gives:
e = so ~ - R~ + 1~ ... 9 ~1 + RJ ~ r J
Hence a correction factor a is:
a = ~ + 4~ ... lo 35~ J
~ - 13 -1 32074~
Thus i~ can be seen that as ~c changes with temperature, the sensed angle will correspondingly change.
It can also be seen that if the capsule is not initially filled to exactly half its volume, an error which is dependent upon the consequent initial difference in liquid leval will result, independently of any temperature induced change in liquid level. This may, however, be compensated for by calibration ac de~cribed below.
In order to compensate for the change in level due to temperature, the sides 9,11 of the capsule moulding 5,7 are chosen to be of a thickness so as to be elastically deformable in response to change in pressure caused by change in volume of the liquid and change in gas vapour pressure within capsule 3 due to change in temperature as illustrated in Figure 7 (for an increase in temperature). For a certain side thickness, the deformation of the sides 5,7 will increase the volume o~
cap6ule 3 to match ~he increased volume of the liquid so as to keep the level of liquid 17 substantially constant, as illustrated by the following exemplary design calculations:
1 3207~8 ASSUMPTIONS
1. That it is necessary to prevent (or reduce to negligible proportions) the variation in liguid lsvel with temperature, within an hermetically sealed, part-filled, cylindrical vessel.
(NB. the principle may be extended to non-cylindrical vessels).
2. That the liquid has a bulk coefficient of thermal expansion which is positive, and significantly greater than that of the vessel.
Optical levels, more commonly called spirit levels, are well known and provide an optical indication of whether or not a sur~ace is horizontal, based on the principle of an air bubble in a liquid-filled vial always seeking the highest point in the vial, the vial being slightly curved so that ~hen at level, the bubble will always take up an equilibrium position. Such bubble levels, if disposed in a suitable ~eame, can also be used to provide an indication of whether or not a surface is vertical.
However, such spirit levels are not capable of measuring deviations ~rom horizontal or vertical outside a very limited range. Also, such spirit levels can be difficult to read accurately as the measurement of level or plumb depends on the ability of the user to determine the position o~ the bubble. Factors such as poor lighting or poor eyesight obviously affect this.
1 3207~8 Electronic spirit levels have been proposed, for example by Cantarella, in U.S. 4 167 818, which uses a capsule part-filled with a conductive liquid. Several electrodes are disposed within the capsule, the resistance between the electrodes being dependent of the position of the liquid within the capsule which, in turn, is dependent upon its inclination. A digital readout of angles of inclination from level and from plumb is provided. However such levels suffer the disadvantage that the accuracy of any measurement from horizontal or vertical is dependent: upon ambient conditions such as temperature, as fluctuations in temperature will lead to variations in the level and resistance of liquid within the capsule which in turn will affect the reading of inclination for angles for which the electrodes are not equally immersed in the liquid.
GB-A-2 071 887 discloses a microwave oven with a separate temperature sensor (28) comprising a bellows (60) and a liquid of a high coefficient of thermal expansion sealed inside, and a sound generating body (54). When the liquid (59) is expanded by heating, the bellows (60) is stretched, causing the sound-g~nerating body (54) to generate a sound which is received by the microwave oven.
GB-A-2 048 473 discloses a thermostat capsule comprising a can (1) of stainless steel with an annular end plate (2) closed by a diaphragm (3). The can (1) is filled with liquid which causes the dapth of the can (1~ to vary with temperature.
US-A-4 028 815 discloses an accelerometer or tilt sensor. It comprises a closed chamber of annular configuration, four electrodes and electrolytic fluid, in conjunction with circuitry arranged to produce an output signal compensated 1 32074~
for temperature variations in impeclance and volume of the fluid.
EP-A-0 035 340 discloses a clinometer comprising a hollow cylindrical housing (10) having a single electrode (12) on one end face and three equal, equally spaced, electrodes (14, 16, 18) on the other end faceO The effects o~ temperature variation are not discussed in it.
According to the invention in a first aspect there is provided an electronic inclinometer incorporating temperature-compensating means and comprising a capsule which is formed as a hollow cylinder and which is part-filled with a liquid, the liquid being such as to vary in volume with variation in temperature, and a plurality oE electrodes connected to the capsule for sensing an electrical characteristic of the liqu.id, said characteristic being one which varies with variation in inclination of the capsule, over at least a certain range of inclination, about a reference axis, so that the inclinometer has an elactrical transfer function which is a function of inclination angle, characterized in that the material and wall thickness of the cylindrical side wall of the capsule are such that the cylindrical side wall does not significantly change dimensionally in response to temperature-induced change in pressure within the capsule and in that the material and wall thickness of each of the end walls are such that the end walls do deform elastically in response to said temperature-induced change in pressure within the capsule so that the internal volume of the capsule is variable in dependance upon temperature, to such an extent that the level of the liquid in the capsule remains substantially constant for any given inclination within said range of inclination with variation in temperature over at least a certain range of temperature.
~' 1 32074~
3a In preferred embodiments: the capsule is formed from plastics material~ more preferably, polybutylene therephthalate, which may be reinforced with glass beads; and the liquid includes methanol.
In further prefsrred embodiments: the capsule comprises first and second mouldings connected together; the capsule may also comprise a hollow cylindrical member and first and second discs, each disc being connected to a respective end of the cylindrical member. The electronic inclinometer may further comprise switch means for connecting the electrodes in a plurality of desired configurations, the s~itch means having an electrical transfer function which i5 a function of temperature. Compensation may be provided for the dependance on temperature of the combined electrical transfer function of the capsule and switch means over the temperature range~
The plurality of electrodes may include first and second electrodes disposed within the capsule, the relative degree of immersion of the first and second electrodes in the liquid ~0 being indicative, within a first angular range, of the angle of inclination of the capsule both about the reference axis and relative to a first reference angle. Further the plurality of electrodes may include third and fourth electrodes disposed within the capsule, the relative degree of immersion of the third and fourth electrodes in the liquid being indicative, within a second angular range~ of the angle of inclination of the capsule both about the reference axis and relative to a second reference angle different from the first reference angle. Moreover, the first and second reference angles may be those at which the first and second electrodes or the third and fourth electrodes, respectively, are equally immersed in the liquid. The first to fourth electrodes may be arranged so tha-t any angle of inclination 3b of the capsula about the reference axis is included within at least one of the first and second ranges. The first and second reference angles may be orthogonally disposed. The first to fourth electrodes may be of substantially semi-circular form and may be spaced one from the other about the raference axis.
According to the invention there is also provided but not claimed in this application a method of calibrating an inclination sensor of the form co~)rising a capsule part filled with a liquid, the position of the liquid within the capsule being indicative of the angle of rotation of the capsule about a reference axis, a plurality o electrodes disposed within the capsule for sensing said position within an angular range, an excitation source, a sensing circuit and means for connecting said electrodes to the sensing circuit and to the excitation ~ource allow measurement of a plurality of electrical characteristics of the liquid which together are indicative of said position, said method comprising the steps of placing the sensor at at least two ~nown angles ~ , measuring the corresponding sensed angles 0 and calculating from the known and sensed angles calibration values a and b where;
O = a ~ + b An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a perspective view of a sensor capsule forming part of an embodiment of the invention;
Figure 2 is a sectional view taken in the plane II~
of Figure l;
1 3207~8 Figure 3 i6 an exyloded sectional view taken through the plane III-III' of Figure l;
Figures 4A-B are sectional views similar to Figure 2 of the capsule at different inclinations;
Figure 5 illustrates the angular range of the sensor.
Fig 6 is a diagram for explaining the effec~ of change in liquid level on capsule sensitivity.
Figure 7 illustrates the ability of the capsule shown in Figures 1 to ~ to compensate for temperature fluctuations.
Figures 8 and 9 are diaqrams illustrating features of the design calculations for calculating a preferred capsule wall thickness, for temperature compensa~ion purposes.
Pigure 10 is a diagram for explaining the effect of switch resistance on capsule sensitivity.
1 3~07~8 Referring to Figures 1 to 3, an inclination sensor, generally designated 1 is shown. The sensor comprises a capsule 3 of generally cylindrical form. The capsule 3 is formed from two engageable non-conductive chemically inert plastics mouldings 5,7 formed preferably from thermoplastic polyester (e.g. a polybutylene terephthalate (PBT) for example VALOX) reinforced with 15-20% glass beads to provide strength and stability.
The mouldings 5, 7 are ultra-sonically welded together to ensure a hermetic seal. The end faces 9,11 of the mouldings 5,7 are formed of a thickness so as to be elastically deformable in response to pressure variations within the capsule 3, as described hereinafter.
Within mouldings 5,7. electrodes A,B and C,D formed from nickel are respectively disposed. Each electrode A-D is of generally semi-circular form and is formed on its respective moulding 5,7 preferably by vacuum deposition or ho~ foil blocking (although it is to be appreciated that other electrode-forming methods may be employed).
The electrodes A,B (or C,D) are separated one from the other by an elongate gap 8 (or 10) so that the electrodes A,B or C,D are not in direct electrical 1 32074~
contact. The gaps 8,10 should be narrow, preferably less than 0.5 mm. Connections to the lelectrodes A-D are provided by means o~ rivets formed from conductivQ plastics material.
which are bonded, preferably by ultra-sonically welding to the case halves; rivets 13,15 for electrodes A,B are shown in Figure 2.
Alternatively, the capsule may be formed from two identical plastics discs, the eleckrodes being formed on the discs by silk screen printing, each disc then being connected to an open axial end of a hollow cylindrical plastics spacer. to form the capsule, the discs being rotated by 90~ relative to one another to give the desired electrode configuration shown in figure 1.
The electrodes A,B are rotated by 90 about a reference axis 0 of the capsule with respect to the electrodes C,D to allow measurement of angles through 360 as described hereinaft~r.
A conductive liquid 17 is disposed within the capsule 3, preferably a mixture of distilled water and methanol and a salt, for example sodium acetate trihydrate (CH3 COONa 3H2O), the capsule 3 being filled, at NTP to half its volume. The remainder of the capsule is filled with air or an inert gas, for example argon.
1 32~74~
The general mode of operation of the capsule is described with reference to Figures 4A and ~B for which a measurement using electrodes A,B as the sensing electrodes is illustrated. Figures 4~ and 4B illustrate the capsule 3 in a schematically shown mounting 19 having an edge 21 which is presented to a surface, the inclination of which is to be measured. One pair of electrodes in this case C,D are coupled together to form a common electrode and an alternating voltage is applied in turn to the electrodes A or B. The impedance and, more particularly, the resistance of the path between electrodes C,D and electrode A or electrode B is dependent upon the degree of immersion of electrode A or electrode B in the conductive liquid 17, the larger degree of immersion, the lower the resistance of the path.
Thus by measuring the resistances of the two paths, between electrodes C,D and electrode A and electrodes C,D and electrode B, the angle o~ inclination ~ of the sensor can be calculated.
,~
1 3207~
More specifically as can be seen by comparison of Figures 4A
and 4B, the total wetted area of electrodes A,B is always substantially a constant, so that, ignoring cross impedances:
ZT Zl Z2 WHERE ZT = The total tesistance of the capsule Zl = The resistance of the path CD to A
Z2 = The resistance of the path CD to B
AND Zl 180 , ZT ... lb 90 + ~
Z2 ~ 180 . ~T ... lc S so - e So, the ratio, R, of the resistances Z1, Z2 is:
...2 2 9o +
hence ~ = go (1 - ~ . 3 ~1 + Rj 1 32074~
Exemplary values of R are as follows:
Table 1 ~ R = ,L
- 50 3.5 1() 0 + 45 0.33 + 50 0.286 Electrodes A,B are used for sensing angles up to t 50 from the hori70ntal in the configuration illustrated in Figures 4A and 4B. For angles of inclination greater than these limits, the electrodes may be reconfigured so that the electrodes A,B become the common electrode and the orthogonally disposed electrodes C,D become the sensing electrodes. the sensor measuring angles in this configuration in the range ~ 50 from vertical.
1 3207~8 Reconfiguring the electrodes may conveniently be performed using a switch matrlx comprising a plurality of analogue switches, for connecting each electrode to an alternating voltage source or to sensing circuitry in common with another electrode, as appropriate.
Use of such electrode switching allows a full 360 of inclination angle to be measured, in terms o~ deviation from level or plumb, (as shown in Figure 5) with the electrode configuration being chosen by computing and control circuitry (not shown) in accordance with the angle of inclination of the sensor. When initialising an inclination measurement, the control circuitry may perform a measurement with an arbitrary pair of electrodes e.g. C,D chosen as the common pair. If the 1~ ratio R calculated by the computing circuitry is within an allowable range (~ 50) (see Table 1), the measurement proceeds whereas if the measured ratio is outside the allowable range, the configuration is changed to connect the other pair of electrodes in common, and the measurement is then performed.
In the described capsule, the volume of the liquid 17 within the capsule 3 is prone to fluctuation with temperature. Due to volume changes arising from differing thermal expansion of the capsule and the liquid, changes in temperature will result in changes in liquid level which will affect: the measurement of inclination. This e~ect is shown with reference to figure 6.
Assuming an increase in liquid level, in response to temperature. Is indicated by change in height x .
Then, let ST be the ~total' conductivity of the half filled capsule:
I -T
~'1' ;' where ZA~ ZB are the resistances of paths CD to A
and CD to B.
1 32074~3 ~z~ ~A SA + SA ~ ~ +~~ + ~ ~ ] ' 5 = S~ E + e + ~1 ... 6 ~ l 90 ~r~
where SA* = the conductance due to plate area A
immersed in the liquid SA = the conductance due to plate area A' immersed in the liquid similarlY Sg = S~ E _ 9O + ~r~ 7 Now R =
Combining 6, 7 and 8 and rearranging gives:
e = so ~ - R~ + 1~ ... 9 ~1 + RJ ~ r J
Hence a correction factor a is:
a = ~ + 4~ ... lo 35~ J
~ - 13 -1 32074~
Thus i~ can be seen that as ~c changes with temperature, the sensed angle will correspondingly change.
It can also be seen that if the capsule is not initially filled to exactly half its volume, an error which is dependent upon the consequent initial difference in liquid leval will result, independently of any temperature induced change in liquid level. This may, however, be compensated for by calibration ac de~cribed below.
In order to compensate for the change in level due to temperature, the sides 9,11 of the capsule moulding 5,7 are chosen to be of a thickness so as to be elastically deformable in response to change in pressure caused by change in volume of the liquid and change in gas vapour pressure within capsule 3 due to change in temperature as illustrated in Figure 7 (for an increase in temperature). For a certain side thickness, the deformation of the sides 5,7 will increase the volume o~
cap6ule 3 to match ~he increased volume of the liquid so as to keep the level of liquid 17 substantially constant, as illustrated by the following exemplary design calculations:
1 3207~8 ASSUMPTIONS
1. That it is necessary to prevent (or reduce to negligible proportions) the variation in liguid lsvel with temperature, within an hermetically sealed, part-filled, cylindrical vessel.
(NB. the principle may be extended to non-cylindrical vessels).
2. That the liquid has a bulk coefficient of thermal expansion which is positive, and significantly greater than that of the vessel.
3. That the gas or vapour filling the remainder of ~he vessel displays a thermal variation of pressure which i~ essentially linear over the working temperature range.
4. That the vessel material is homogeneous, isotropic and has a single, positive value of thermal expansivity.
(NB. The principle may still be employed if this assumption is not met, but the design calculations Iwould become more involved).
?
, . ~
~, 1 32074~
For this particular design, the cylindrical vessel is mounted with the axis horizontal. The ve6sel walls are thin in relatiom to the vessel size and are not stressed beyond the elastic limit. All deflec~ions are small.
The cylindrical vessel has a diameter D = 50 mm and an axial length L = lOmm DESIGN CALCULATIONS
1. Differential thermal e~pansion Consider a cylindrical vessel of diameter D, of unit axial length and illed to a diameter with liquid of bulk thermal expansion coefficient ef. The ves~el is made of material having a linear expansion coefficient f ev as illustrated in figure 8.
The linear expansion coefficient is defined such ~hat at temperature T ~ ~T, diameter = D ~1 ~ ev~T) and the bulk coefficient of the liquid similarly:
volume = V (1 ~ e~T) where V = initial volume at tempera~ure T.
Now vess,el volume at T
1 3207~3 new volume at T -~ ~T
= _ [D(l -~ ev ~T)] (1 -~ ev~T) = ~D (1 + ev~T) ~11) Original liquid volume at T
New liquid volume = ~D (1 + ef ~T) . . liquid rises in vessel by a heigh~ given by:-new liquid volume - 1/2 of new vessel volume new X-sectional area at diameter (NB This assumes that variations în liquid level are small).
.-. liquid level rise = D (1 + ef~T~ - D (1 ~ ev~T) D. (1 + ev~T) = ~D ~1 + ef~T - (1 + ev~T) ]
. . .
(1 ~ ev~T) expanding, and neglecting pOWeLS of efand ev, = D [e~T - 3ev~T] (12) 1 + 2 ev~T
which is approximatelyO
~D ~T (ef - 3ev) 8 (13) (since 2.ev~T < 1) Note that 3 ev = bulk expansion coefficient of the vessel 1 3207~3 2) Ve6sel bulging due to internal pressure ~or a f lat circular plate, simply-supported at the circumference, the deflection at any point at radiu~
r from the centre, is given by:-Y = 3. P a2 (1 - vZ) r~5-~v ~ ~ r4 - ~3~ rZ
8 E t3 L2 ( l~v) 2a2 ( l+v) (REF POARK. Formula6 for stree and strain (McGraw Hill, 4th Editi.on) Page 216, Case 1) where P = internal pressure a = radius of plate E = Youngs modulus of plate material t = plate thickness v = pois60n6 ration of.plate material (as6umes material is isotropic) The incremental volume due to this deflection is given by:-r=a 2~ ~ y.r.dr r=O (15 (See figure 9) Assuming that pres6ure~temperature is given by thegas laws:-P2 = T2 Pl Tl or Pl = Pl T2 T
or P = P2 ~ P
Tl J~ 1 Pl/K (for small temperature changes) As6uming that Tl = 20 = 293K) bulge volume, as a function of temperature isgiven by:-1 3207~8 r=a Z1r 3 Pl a2 (l-vZ) ~I (5~v) a2 ~ r4 _ (3~ 2 I r.dr 293 a E. t3 J ¦_ 2(1-~v) 2a2 (l~v) _¦
r=0 (mm /K~
Substituting values:-Pl = O.l N/mm ~= 1 bar) a a 25 mm v ~0.4 (for polyester. ref KEMPE'S) E ~~Z300 N/mm (for VALOX material nominal value) and integrating gives:-2~r 3 0.1 Z5 ._0.84 ~ 1205r + r - 2.429r dr 293 8 2300 t3 J 1250 = 183.559 1 1205rZ + r - r lo6 t3 - Z 7500 1.6468_ = 31.56 mm /K
t3 (16) 3) Equate thermal expansion to ves6el bulging.
Taking expansivity values of exemplary materials used: -6 For methanol: ef = 1190 .lO (BULK) For VALOX : ey = 70 .10 (LINEAR) (nominal value) Differential volume change due to ~hermal expansion = liquid height change x d~ametrial cross-section = 7r D (1190 - 3.70) .10 .D.L (from (13)) where L axial length of vessel = lO mm.
= ~.50 .10 (1190 - 210) 8.10 9.621 mm /K
, . ~
9.~1 = 31.~6 ,~
t = ~1.56 '~ .6~1 t = ~ . ~86 mm The calculations assume that there is negLigible pressure bulging of the cylindrical wall of the vessel and that both 1~ circular walls are of equal thickness.
The principle can still be employed if these assumptions are not met.
L~ Fo~ ease of calculation, it has been assumed that the capsule walls are simply-supported at the circumference and of uniform thickness. More refined analysis may be car~ied ou~ within the ability of one skilled in the art by, for example, finite element techniques to provide a more accu~ate determination of equation 14 for a pacticular application.
2~ It is to be appreciated that this principle is usable in applications other than for the inclination sensor described, 1 3207~8 The above compensation technique may be f~lrther employed to give added temperature compensation for other elements in the inclination sensor. More particularly, if the sensor is used to measure angles outside the range of electrodes AB by employing electrode switching to measure, for example, a full 360 of inclination angle as previously described, if electronic switches to perforrn the electrode switching formed as part of an application speciEic integrated 1~ circuit (ASIC), for example, are used for such switching, then the resistance of the switches will tend to change with eemperature.
Such resistance contributes co the total resistance of the sensor as measured, and thus the computing and control circuitry needs to be calibrated to take the switch resistance into account (as described below).
Such calibration cannot, however, compensate for temperature - induced resistance fluctuation, without the use of a temperature sensor and a sizable increase 2~ in calibration memory capacity.
The effecc of switch resistance on measured angle will be illustrated with reference to figure lO. For any usable electrode configuration, an analogue swicch having a resistance rSW will be connected to each electrode, thus modifying the total sensed resistance ratio (R) of the capsule as follows:
1 3207~8 R 1 = 1sw 2 2rsw + Zl ~.. 17 = 2rsw + 2ZT
... 1~
2~sw2ZT (from equation lb ~ lc) 1+ 9 Expanding and rearranging, it can be shown that ~2 ~a(R~l 1)~ ~ 9 3 -(R-1_1) (1-~a) = 0 .. 19 WHERE = rSw T ... 20 Solving as a quadratic equation in 6 and letting:
go (R-l - 1) (R + 1~ ... 21 (From equation 3 letting R = 1, ~ being the computer angle) R
- 1 3207~8 1 + 4 ~ (1 + ~)/~'~
- -- - ... 22 2~ , ~' As a and ~ have the same sign, and since a < C
l, using a Taylor expansion:
1 +1 + 2 ~ (l + ~ )(~ ) 2~ ~, 909~) (1 +rx) E1 15 The term (l+ r ) is dependent upon temperature Zr due to fluctuation in rSw as mentioned above and also due to fluctuation in to~al capsule resistance ZT
However it can be seen that the total angular-dependent compensation factor a for liquid level and for switch resistance is:
a = 1-~ 4 x ~, r ~ r ~w ... 24 25 As previously discussed, the capsule can be designed to deform, to that 4 x remains con6tant. However, ~r r 1 3207~
the capsule can further be made to deform to compensate, to some extent for changes in rSw , so that the ZT
temperature dependence of the compensation factor a is reduced still further. In this case, the level of liquid in the capsule will fluctuate slightly with temperature in order to provide the additional compensation for the s~itch and liquid resistance change.
For example, the compensation factor a~ay be rewritten in temperature dependent form as:
a = ~s,20 ( _~ _ + 4 x ~T ... 25 ZT,,0 (1 + ~ ~ T) ~ r where ~ T represents a change in temperature from the measured values of rSW and ZT at a given temperature (20 in this example) and x is the temperature dependent change in liquid level in mm/K.
For perfect temperature compensation:
s,20 + 4 x ~ T rs,20 ... '6 ZT,20 74a which glves:
s,20 rr [ 1 - (l +~T) (l - ~QT) ] ... 27 ZT,20 T 4 for small a, ~
tr rs 20 ( ~ ) r mm/K. ,.. 28 ZT,20 a and ~ may be ~ound by experimentation so that the desired value ~or x may be calculated and the capsule geometry designed to provide the necessary compensation for the non-zero heiyht change x , in a similar manner to that described with reference to equatio~ 11 to 16.
In general, the capsule can be designed to deform in response to temperature to maintain the electrical transfer Eunction of the capsule and any external sensor circuitry independent of temperature or at least to provide a l'best fitll over a desired temperature range.
In such a case, the temperature dependence of a capsule could be established empirically and the capsule design modified to pcovide the most useful compensation, in the manner previously described.
As described above, initial conditions (independen~ of temperature induced change) exist in the capsule and sensor, and the capsule and sensor need to be calibrated `
to take these initial conditions into account.
1 32074~3 In general, the angle sensed by the capsule described above and associated sensor circuitry (~'~ is related to the actual angle of inclination ~e) by the following e~pression:
e = C0 ~ Cl e + C2 e 2 + C3 e 3 ~ ........ Cn e n ... 29 = a 0 + b ... 30 where a* = Cl ~ C2 e + C3 e 2 + .. Cn e' (n+l) ...31 b = C0 ... 32 The calibration factors a* and b are dependent, to some extent, on the position of the electrodes within the capsule and any errors in the placement of the electrodes will result in changes in the calibraton factors, so that different factors a*, b usually exist for each pair of slectrodes A, B or C, D.
The inventors have found that the dominant influence affecting calibration ~actor a* is related to the variation in initial liquid level with respect to the measurin~
electrodes which is linearly related to angle as is apparent from equation 10. The coefficients C2-CN are, consequently, small in comparison to Cl for capsules with reasonable manufacturing tolerances.
X
Thus, it can be seen from equation 26 that with this approximation ~he actual angle e i5 a linear function of sensed angle e .
Thus, if O is plotted against e , the gradient of the resulting straight line will give a . Thus, by placing the capsule at two, known angles el, ~2 measuring the corresponding sensed angles el, e2 will provide sufficient data for establishing the gradient: of the straight line between these two points and so will give a*.
Then by applying the initial condition that ~ = e at the origin (0), b can then be calculated as follows:
O = e = a* e' + b => b = -a* e' (e = o) ...33 As the calibration factor b is dependent upon the electrode-to-measuring surface relationship, if the capsule is inverted, the sign of the calibration parameter b needs to be changed to provide the appropriate compensation.
At the manufacturing stage, the values of a and b may be stored in a programmable read only memory (PROM) for use by the computing and control circuitry when calculating the actual inclination angle.
X
1 320~
When calculating a for the capsule of figure 1, preferably the known angles are chosen as ~ 45. This difference in angles is chosen as it will be appreciated that although the terms C2-CN are small, they do have some ef~ect upon the measurement o angle. By choosing actual angles at opposed ends of the available angular range of the pair of plates, and by forcing the resulting straight line graph through the origin (0 =
O = 0 (equation 33)), a reasonable spread of calibration compensation is given over the whole sensing range.
It will be noted that electrode configuration of plates A, B (for example) is usable to measure either 0 or 180, depending upon whether the inclination measuring surface 21 is upside down or the right way up. In orde~
to distinguish between these two conditions (or any other equivalent condition) in which identical areas o~
electrodes A and B are immersed in the liquid and w~e~e the difference in angular position depends upon the dispo6ition o~ the surface 21, additional information concerning which of the two possible angles the inclination the measuring device is inclined at may be obtained by measuring the same angle for electrodes C
and D. It can be seen that the position of the liquid relative to plates C and D will be different for the ~o "equivalent~ inclinations m~asurable using pla~es A and B.
1 3207~8 For the electrode arrangement as shown in the capsule of figures 1 and 8 the following relationship holds:
Table 3 Measuring Ran e Non Measuring Polarity of ~ngular Electrodes Electrodes Measurement for Non Measuring Electrodes _~
(i) A,B 50c-<-50 C,D - ve (ii) A,B =>130;e<-130 C,D + ve (iii) C,D -140<ec-40 A,B - ve (iv) C,D 40<e<l40 A,B + ve This relationship may then be used to enable the computing circuitry to decide whether or not the factor b should be added or subtracted.
~0
(NB. The principle may still be employed if this assumption is not met, but the design calculations Iwould become more involved).
?
, . ~
~, 1 32074~
For this particular design, the cylindrical vessel is mounted with the axis horizontal. The ve6sel walls are thin in relatiom to the vessel size and are not stressed beyond the elastic limit. All deflec~ions are small.
The cylindrical vessel has a diameter D = 50 mm and an axial length L = lOmm DESIGN CALCULATIONS
1. Differential thermal e~pansion Consider a cylindrical vessel of diameter D, of unit axial length and illed to a diameter with liquid of bulk thermal expansion coefficient ef. The ves~el is made of material having a linear expansion coefficient f ev as illustrated in figure 8.
The linear expansion coefficient is defined such ~hat at temperature T ~ ~T, diameter = D ~1 ~ ev~T) and the bulk coefficient of the liquid similarly:
volume = V (1 ~ e~T) where V = initial volume at tempera~ure T.
Now vess,el volume at T
1 3207~3 new volume at T -~ ~T
= _ [D(l -~ ev ~T)] (1 -~ ev~T) = ~D (1 + ev~T) ~11) Original liquid volume at T
New liquid volume = ~D (1 + ef ~T) . . liquid rises in vessel by a heigh~ given by:-new liquid volume - 1/2 of new vessel volume new X-sectional area at diameter (NB This assumes that variations în liquid level are small).
.-. liquid level rise = D (1 + ef~T~ - D (1 ~ ev~T) D. (1 + ev~T) = ~D ~1 + ef~T - (1 + ev~T) ]
. . .
(1 ~ ev~T) expanding, and neglecting pOWeLS of efand ev, = D [e~T - 3ev~T] (12) 1 + 2 ev~T
which is approximatelyO
~D ~T (ef - 3ev) 8 (13) (since 2.ev~T < 1) Note that 3 ev = bulk expansion coefficient of the vessel 1 3207~3 2) Ve6sel bulging due to internal pressure ~or a f lat circular plate, simply-supported at the circumference, the deflection at any point at radiu~
r from the centre, is given by:-Y = 3. P a2 (1 - vZ) r~5-~v ~ ~ r4 - ~3~ rZ
8 E t3 L2 ( l~v) 2a2 ( l+v) (REF POARK. Formula6 for stree and strain (McGraw Hill, 4th Editi.on) Page 216, Case 1) where P = internal pressure a = radius of plate E = Youngs modulus of plate material t = plate thickness v = pois60n6 ration of.plate material (as6umes material is isotropic) The incremental volume due to this deflection is given by:-r=a 2~ ~ y.r.dr r=O (15 (See figure 9) Assuming that pres6ure~temperature is given by thegas laws:-P2 = T2 Pl Tl or Pl = Pl T2 T
or P = P2 ~ P
Tl J~ 1 Pl/K (for small temperature changes) As6uming that Tl = 20 = 293K) bulge volume, as a function of temperature isgiven by:-1 3207~8 r=a Z1r 3 Pl a2 (l-vZ) ~I (5~v) a2 ~ r4 _ (3~ 2 I r.dr 293 a E. t3 J ¦_ 2(1-~v) 2a2 (l~v) _¦
r=0 (mm /K~
Substituting values:-Pl = O.l N/mm ~= 1 bar) a a 25 mm v ~0.4 (for polyester. ref KEMPE'S) E ~~Z300 N/mm (for VALOX material nominal value) and integrating gives:-2~r 3 0.1 Z5 ._0.84 ~ 1205r + r - 2.429r dr 293 8 2300 t3 J 1250 = 183.559 1 1205rZ + r - r lo6 t3 - Z 7500 1.6468_ = 31.56 mm /K
t3 (16) 3) Equate thermal expansion to ves6el bulging.
Taking expansivity values of exemplary materials used: -6 For methanol: ef = 1190 .lO (BULK) For VALOX : ey = 70 .10 (LINEAR) (nominal value) Differential volume change due to ~hermal expansion = liquid height change x d~ametrial cross-section = 7r D (1190 - 3.70) .10 .D.L (from (13)) where L axial length of vessel = lO mm.
= ~.50 .10 (1190 - 210) 8.10 9.621 mm /K
, . ~
9.~1 = 31.~6 ,~
t = ~1.56 '~ .6~1 t = ~ . ~86 mm The calculations assume that there is negLigible pressure bulging of the cylindrical wall of the vessel and that both 1~ circular walls are of equal thickness.
The principle can still be employed if these assumptions are not met.
L~ Fo~ ease of calculation, it has been assumed that the capsule walls are simply-supported at the circumference and of uniform thickness. More refined analysis may be car~ied ou~ within the ability of one skilled in the art by, for example, finite element techniques to provide a more accu~ate determination of equation 14 for a pacticular application.
2~ It is to be appreciated that this principle is usable in applications other than for the inclination sensor described, 1 3207~8 The above compensation technique may be f~lrther employed to give added temperature compensation for other elements in the inclination sensor. More particularly, if the sensor is used to measure angles outside the range of electrodes AB by employing electrode switching to measure, for example, a full 360 of inclination angle as previously described, if electronic switches to perforrn the electrode switching formed as part of an application speciEic integrated 1~ circuit (ASIC), for example, are used for such switching, then the resistance of the switches will tend to change with eemperature.
Such resistance contributes co the total resistance of the sensor as measured, and thus the computing and control circuitry needs to be calibrated to take the switch resistance into account (as described below).
Such calibration cannot, however, compensate for temperature - induced resistance fluctuation, without the use of a temperature sensor and a sizable increase 2~ in calibration memory capacity.
The effecc of switch resistance on measured angle will be illustrated with reference to figure lO. For any usable electrode configuration, an analogue swicch having a resistance rSW will be connected to each electrode, thus modifying the total sensed resistance ratio (R) of the capsule as follows:
1 3207~8 R 1 = 1sw 2 2rsw + Zl ~.. 17 = 2rsw + 2ZT
... 1~
2~sw2ZT (from equation lb ~ lc) 1+ 9 Expanding and rearranging, it can be shown that ~2 ~a(R~l 1)~ ~ 9 3 -(R-1_1) (1-~a) = 0 .. 19 WHERE = rSw T ... 20 Solving as a quadratic equation in 6 and letting:
go (R-l - 1) (R + 1~ ... 21 (From equation 3 letting R = 1, ~ being the computer angle) R
- 1 3207~8 1 + 4 ~ (1 + ~)/~'~
- -- - ... 22 2~ , ~' As a and ~ have the same sign, and since a < C
l, using a Taylor expansion:
1 +1 + 2 ~ (l + ~ )(~ ) 2~ ~, 909~) (1 +rx) E1 15 The term (l+ r ) is dependent upon temperature Zr due to fluctuation in rSw as mentioned above and also due to fluctuation in to~al capsule resistance ZT
However it can be seen that the total angular-dependent compensation factor a for liquid level and for switch resistance is:
a = 1-~ 4 x ~, r ~ r ~w ... 24 25 As previously discussed, the capsule can be designed to deform, to that 4 x remains con6tant. However, ~r r 1 3207~
the capsule can further be made to deform to compensate, to some extent for changes in rSw , so that the ZT
temperature dependence of the compensation factor a is reduced still further. In this case, the level of liquid in the capsule will fluctuate slightly with temperature in order to provide the additional compensation for the s~itch and liquid resistance change.
For example, the compensation factor a~ay be rewritten in temperature dependent form as:
a = ~s,20 ( _~ _ + 4 x ~T ... 25 ZT,,0 (1 + ~ ~ T) ~ r where ~ T represents a change in temperature from the measured values of rSW and ZT at a given temperature (20 in this example) and x is the temperature dependent change in liquid level in mm/K.
For perfect temperature compensation:
s,20 + 4 x ~ T rs,20 ... '6 ZT,20 74a which glves:
s,20 rr [ 1 - (l +~T) (l - ~QT) ] ... 27 ZT,20 T 4 for small a, ~
tr rs 20 ( ~ ) r mm/K. ,.. 28 ZT,20 a and ~ may be ~ound by experimentation so that the desired value ~or x may be calculated and the capsule geometry designed to provide the necessary compensation for the non-zero heiyht change x , in a similar manner to that described with reference to equatio~ 11 to 16.
In general, the capsule can be designed to deform in response to temperature to maintain the electrical transfer Eunction of the capsule and any external sensor circuitry independent of temperature or at least to provide a l'best fitll over a desired temperature range.
In such a case, the temperature dependence of a capsule could be established empirically and the capsule design modified to pcovide the most useful compensation, in the manner previously described.
As described above, initial conditions (independen~ of temperature induced change) exist in the capsule and sensor, and the capsule and sensor need to be calibrated `
to take these initial conditions into account.
1 32074~3 In general, the angle sensed by the capsule described above and associated sensor circuitry (~'~ is related to the actual angle of inclination ~e) by the following e~pression:
e = C0 ~ Cl e + C2 e 2 + C3 e 3 ~ ........ Cn e n ... 29 = a 0 + b ... 30 where a* = Cl ~ C2 e + C3 e 2 + .. Cn e' (n+l) ...31 b = C0 ... 32 The calibration factors a* and b are dependent, to some extent, on the position of the electrodes within the capsule and any errors in the placement of the electrodes will result in changes in the calibraton factors, so that different factors a*, b usually exist for each pair of slectrodes A, B or C, D.
The inventors have found that the dominant influence affecting calibration ~actor a* is related to the variation in initial liquid level with respect to the measurin~
electrodes which is linearly related to angle as is apparent from equation 10. The coefficients C2-CN are, consequently, small in comparison to Cl for capsules with reasonable manufacturing tolerances.
X
Thus, it can be seen from equation 26 that with this approximation ~he actual angle e i5 a linear function of sensed angle e .
Thus, if O is plotted against e , the gradient of the resulting straight line will give a . Thus, by placing the capsule at two, known angles el, ~2 measuring the corresponding sensed angles el, e2 will provide sufficient data for establishing the gradient: of the straight line between these two points and so will give a*.
Then by applying the initial condition that ~ = e at the origin (0), b can then be calculated as follows:
O = e = a* e' + b => b = -a* e' (e = o) ...33 As the calibration factor b is dependent upon the electrode-to-measuring surface relationship, if the capsule is inverted, the sign of the calibration parameter b needs to be changed to provide the appropriate compensation.
At the manufacturing stage, the values of a and b may be stored in a programmable read only memory (PROM) for use by the computing and control circuitry when calculating the actual inclination angle.
X
1 320~
When calculating a for the capsule of figure 1, preferably the known angles are chosen as ~ 45. This difference in angles is chosen as it will be appreciated that although the terms C2-CN are small, they do have some ef~ect upon the measurement o angle. By choosing actual angles at opposed ends of the available angular range of the pair of plates, and by forcing the resulting straight line graph through the origin (0 =
O = 0 (equation 33)), a reasonable spread of calibration compensation is given over the whole sensing range.
It will be noted that electrode configuration of plates A, B (for example) is usable to measure either 0 or 180, depending upon whether the inclination measuring surface 21 is upside down or the right way up. In orde~
to distinguish between these two conditions (or any other equivalent condition) in which identical areas o~
electrodes A and B are immersed in the liquid and w~e~e the difference in angular position depends upon the dispo6ition o~ the surface 21, additional information concerning which of the two possible angles the inclination the measuring device is inclined at may be obtained by measuring the same angle for electrodes C
and D. It can be seen that the position of the liquid relative to plates C and D will be different for the ~o "equivalent~ inclinations m~asurable using pla~es A and B.
1 3207~8 For the electrode arrangement as shown in the capsule of figures 1 and 8 the following relationship holds:
Table 3 Measuring Ran e Non Measuring Polarity of ~ngular Electrodes Electrodes Measurement for Non Measuring Electrodes _~
(i) A,B 50c-<-50 C,D - ve (ii) A,B =>130;e<-130 C,D + ve (iii) C,D -140<ec-40 A,B - ve (iv) C,D 40<e<l40 A,B + ve This relationship may then be used to enable the computing circuitry to decide whether or not the factor b should be added or subtracted.
~0
Claims (16)
1. An electronic inclinometer incorporating temperature-compensating means and comprising a capsule which is formed as a hollow cylinder and which is part-filled with a liquid, the liquid being such as to vary in volume with variation in temperature, and a plurality of electrodes connected to the capsule for sensing an electrical characteristic of the liquid, said characteristic being one which varies with variation in inclination of the capsule, over at least a certain range of inclination, about a reference axis, so that the inclinometer has an electrical transfer function which is a function of inclination angle, characterized in that the material and wall thickness of the cylindrical side wall of the capsule are such that the cylindrical side wall does not significantly change dimensionally in response to temperature-induced change in pressure within the capsule and in that the material and wall thickness of each of the end walls are such that the end walls do deform elastically in response to said temperature-induced change in pressure within the capsule so that the internal volume of the capsule is variable in dependance upon temperature, to such an extent that the level of the liquid in the capsule remains substantially constant for any given inclination within said range of inclination with variation in temperature over at least a certain range of temperature.
2. An electronic inclinometer as claimed in claim 1, wherein the capsule is formed from plastics material.
3. An electronic inclinometer as claimed in claim 2, wherein the plastics material is a polybutylene terephthalate.
4. An electronic inclinometer as claimed in claim 2, wherein the plastics material is reinforced with glass beads.
5. An electronic inclinometer as claimed in claim 1, wherein the liquid comprises methanol.
6. An electronic inclinometer as claimed in any one of claims 1 to 5, wherein the capsule comprises first and second mouldings connected together.
7. An electronic inclinometer as claimed in any one of claims 1 to 5, wherein the capsule comprises a hollow cylindrical member and first and second discs, each disc being connected to a respective end of the cylindrical member.
8. An electronic inclinometer as claimed in claim 1, and further comprising switch means for connecting the electrodes in a plurality of desired configurations, the switch means having an electrical transfer function which is a function of temperature.
9. An electronic inclinometer as claimed in claim 8, wherein compensation is provided for the dependance on temperature of the combined electrical transfer function of the capsule and switch means over said temperature range.
10. An electronic inclinometer as claimed in claim 1, wherein said plurality of electrodes includes first and second electrodes disposed within the capsule, the relative degree of immersion of the first and second electrodes in the liquid being indicative, within a first angular range, of the angle of inclination of the capsule both about the reference axis and relative to a first reference angle.
11. An electronic inclinometer as claimed in claim 10, wherein said plurality of electrodes includes third and fourth electrodes disposed within the capsule, the relative degree of immersion of the third and fourth electrodes in the liquid being indicative, within a second angular range, of the angle of inclination of the capsule both about the reference axis and relative to a second reference angle different from the first reference angle.
12. An electronic inclinometer as claimed in claim 11, wherein the first and second reference angles are those at which the first and second electrodes or the third and fourth electrodes, respectively, are equally immersed in the liquid.
13. An electronic inclinometer as claimed in claim 11, wherein the first to fourth electrodes are arranged so that any angle of inclination of the capsule about the reference axis is included within at least one of the first and second ranges.
14. An electronic inclinometer as claimed in claim 11, wherein the first and second reference angles are orthogonally disposed.
15. An electronic inclinometer as claimed in any one of claims 10 to 14, wherein the first and second electrodes are of substantially semi-circular form and are spaced one from the other about the reference axis.
16. An electronic inclinometer as claimed in any one of claims 11 to 14, wherein the third and fourth electrodes are of substantially semi-circular form and are spaced one from the other about the reference axis.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000616623A CA1330873C (en) | 1986-01-23 | 1993-04-28 | Inclination measuring device and a capsule therefor |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8601586 | 1986-01-23 | ||
| GB8601586A GB2186693B (en) | 1986-01-23 | 1986-01-23 | Inclination sensor |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000616623A Division CA1330873C (en) | 1986-01-23 | 1993-04-28 | Inclination measuring device and a capsule therefor |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1320748C true CA1320748C (en) | 1993-07-27 |
Family
ID=10591808
Family Applications (3)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000527959A Expired - Fee Related CA1292049C (en) | 1986-01-23 | 1987-01-22 | Inclination measuring device |
| CA000527960A Expired - Fee Related CA1320748C (en) | 1986-01-23 | 1987-01-22 | Inclination measuring device and a capsule therefor |
| CA000616623A Expired - Fee Related CA1330873C (en) | 1986-01-23 | 1993-04-28 | Inclination measuring device and a capsule therefor |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000527959A Expired - Fee Related CA1292049C (en) | 1986-01-23 | 1987-01-22 | Inclination measuring device |
Family Applications After (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000616623A Expired - Fee Related CA1330873C (en) | 1986-01-23 | 1993-04-28 | Inclination measuring device and a capsule therefor |
Country Status (9)
| Country | Link |
|---|---|
| US (2) | US5170567A (en) |
| EP (2) | EP0291507B1 (en) |
| JP (2) | JP2785934B2 (en) |
| KR (2) | KR950014819B1 (en) |
| CN (2) | CN87100814A (en) |
| CA (3) | CA1292049C (en) |
| DE (2) | DE3774120D1 (en) |
| GB (2) | GB2186693B (en) |
| WO (2) | WO1987004515A1 (en) |
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| DE102005025908B3 (en) * | 2005-06-06 | 2006-11-09 | Hahn-Schickard-Gesellschaft für angewandte Forschung e.V. | Capacitative sensor to measure values, e.g. for vehicle tilts and automatic machines, has two electrode pairs with a moving component between them with measurement of difference capacities at part-capacitors formed by the electrode array |
| JP5264497B2 (en) | 2005-12-02 | 2013-08-14 | エー． デニッシュ，リー | Shape / acceleration measuring instrument and apparatus |
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| CN102564398B (en) * | 2011-12-29 | 2013-09-18 | 东南大学 | Micro mechanical capacitor type dip sensor |
| KR200471538Y1 (en) | 2013-11-08 | 2014-02-28 | 이재석 | Dice having angle measuring function |
| CZ309210B6 (en) * | 2013-11-15 | 2022-05-25 | Linet, Spol. S R. O. | Bed with tilt indicator |
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| WO2016141360A1 (en) * | 2015-03-04 | 2016-09-09 | California Institute Of Technology | Position sensing and guiding system |
| US10088311B2 (en) * | 2016-09-15 | 2018-10-02 | Texas Instruments Incorporated | Analog floating-gate inclinometer |
| CN106595590B (en) * | 2016-12-13 | 2019-04-30 | 武汉理工大学 | A kind of dual-axis inclinometer based on balance rod principle |
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| US2584917A (en) * | 1950-10-09 | 1952-02-05 | Edward D Powell | Level |
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| JPS61193015A (en) * | 1985-01-31 | 1986-08-27 | ルーカス・インダストリーズ・インコーポレイテッド | Inclinometer |
-
1986
- 1986-01-23 GB GB8601586A patent/GB2186693B/en not_active Expired - Lifetime
-
1987
- 1987-01-22 CA CA000527959A patent/CA1292049C/en not_active Expired - Fee Related
- 1987-01-22 CA CA000527960A patent/CA1320748C/en not_active Expired - Fee Related
- 1987-01-23 DE DE8787900859T patent/DE3774120D1/en not_active Expired - Fee Related
- 1987-01-23 US US07/223,241 patent/US5170567A/en not_active Expired - Fee Related
- 1987-01-23 EP EP87900859A patent/EP0291507B1/en not_active Expired - Lifetime
- 1987-01-23 KR KR1019870700860A patent/KR950014819B1/en not_active IP Right Cessation
- 1987-01-23 KR KR1019870700868A patent/KR960013449B1/en not_active IP Right Cessation
- 1987-01-23 EP EP87900858A patent/EP0290452B1/en not_active Expired - Lifetime
- 1987-01-23 DE DE8787900858T patent/DE3770461D1/en not_active Expired - Fee Related
- 1987-01-23 CN CN198787100814A patent/CN87100814A/en active Pending
- 1987-01-23 JP JP62500893A patent/JP2785934B2/en not_active Expired - Lifetime
- 1987-01-23 US US07/223,240 patent/US5172481A/en not_active Expired - Fee Related
- 1987-01-23 WO PCT/GB1987/000042 patent/WO1987004515A1/en active IP Right Grant
- 1987-01-23 CN CN198787100808A patent/CN87100808A/en active Pending
- 1987-01-23 WO PCT/GB1987/000041 patent/WO1987004514A1/en active IP Right Grant
- 1987-01-23 JP JP62500889A patent/JP2634832B2/en not_active Expired - Lifetime
-
1989
- 1989-11-10 GB GB8925486A patent/GB2222686B/en not_active Expired - Lifetime
-
1993
- 1993-04-28 CA CA000616623A patent/CA1330873C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| KR960013449B1 (en) | 1996-10-05 |
| WO1987004515A1 (en) | 1987-07-30 |
| EP0290452B1 (en) | 1991-05-29 |
| JPH01501415A (en) | 1989-05-18 |
| KR950014819B1 (en) | 1995-12-15 |
| EP0291507A1 (en) | 1988-11-23 |
| EP0291507B1 (en) | 1991-10-23 |
| GB2186693A (en) | 1987-08-19 |
| US5172481A (en) | 1992-12-22 |
| WO1987004514A1 (en) | 1987-07-30 |
| GB2222686B (en) | 1990-08-29 |
| DE3774120D1 (en) | 1991-11-28 |
| CN87100808A (en) | 1987-09-02 |
| KR880700925A (en) | 1988-04-13 |
| CN87100814A (en) | 1987-12-02 |
| KR880700924A (en) | 1988-04-13 |
| DE3770461D1 (en) | 1991-07-04 |
| CA1292049C (en) | 1991-11-12 |
| JP2785934B2 (en) | 1998-08-13 |
| CA1330873C (en) | 1994-07-26 |
| GB2186693B (en) | 1990-09-05 |
| GB8925486D0 (en) | 1989-12-28 |
| GB2222686A (en) | 1990-03-14 |
| JPH01501414A (en) | 1989-05-18 |
| EP0290452A1 (en) | 1988-11-17 |
| US5170567A (en) | 1992-12-15 |
| GB8601586D0 (en) | 1986-02-26 |
| JP2634832B2 (en) | 1997-07-30 |
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